Michael Farrell was head of the Centers for Disease Control and Prevention lab since 2009. He submitted his resignation Tuesday, the spokesman said.

Farrell was reassigned following an incident last month at an Atlanta lab that handles bioterrorism agents. The lab was supposed to completely kill anthrax samples before sending them to two other CDC labs that had fewer safeguards, but didn't.

Dozens of CDC workers were potentially exposed to anthrax. No one got sick. But an internal investigation found serious safety lapses, including use of an unapproved sterilization technique and improper use of a potent type of anthrax.

The CDC fell under a harsh spotlight following the incident and the subsequent disclosure of another safety breach at the agency's influenza laboratory in which relatively harmless avian flu virus was accidentally contaminated with a much deadlier strain. The contaminated virus was then sent to a lab run by the U.S. Department of Agriculture.